1. Field of the Invention
The present invention relates to an information processing apparatus, an information processing system, an information processing method, and a computer program product.
2. Description of the Related Art
A sheet conveyance device, such as an automatic document feeder (ADF), is configured to periodically convey sheets one by one. In some cases, however, trouble occurs that the sheets attract each other due to, for example, static electricity or humidity, and thus, two or more sheets are conveyed in an overlapping manner (hereinafter, referred to as multi-feed). Hence, conventional sheet conveyance devices use methods for detecting the multi-feed using dedicated sensors. For example, a technique is already known that detects a multi-feed state by disposing an ultrasonic sensor so as to interpose the sheet therein, and detecting the paper thickness based on a difference in received signal between a case in which one sheet is conveyed and a case in which multiple sheets are fed.
As a technique for detecting the multi-feed using image processing, for example, an invention disclosed in Japanese Unexamined Patent Application Publication No. 2004-186807 is known. According to this invention, the multi-feed of form sheets is detected using a scanned image of the sheet(s). Specifically, edges, each including a predefined straight line component, of the sheet(s) are detected from the image supplied from the scanner, so as to detect the multi-feed of the form sheets based on the inclination of each of the edges.
However, when two sheets are conveyed in an unaligned state, conventional multi-feed detection mechanisms are sometimes incapable of correctly measuring the paper thickness, and thereby are incapable of detecting the multi-feed. In addition, a sensor dedicated to the multi-feed detection is required, so that the cost of an overall system increases. The known example described above detects the multi-feed by analyzing the image read by the scanner using image processing without providing a dedicated sensor, and is incapable of detecting the multi-feed when the two sheets have the same inclination.